Apparatus for supersonic examination of bodies



Aug. 26, 1958 E. E. SHELDON 1 2,848,890

APPARATUS FOR SUPERSONIC EXAMINATION OF BODIES Filed May 7, 1952 3 Sheets-Sheet 2 a; LIGHT L 6? 6! 14 404' ial Aug. 26, 1958 E. E. SHELDON 2,848,890

APPARATUS FOR SUPERSONIC EXAMINATION OF BODIES Filed May 7, 1952 s Sheets-Sheet s 1 32 I I: 114.] 0z

[D i V K i Tag [I {U I w [60 [l] L- [I so'uizcs OF" L:- TIMER AMPu- FIER J OUECE or POTENTIAL INVENTOR. {DMZ/FD 461mm 59mm United States Patent Ufiice 2,848,890 Patented Aug. 26, 195.8

' .APPAR A-IEUS :FQR JSIJPERSONIC EX M NATION YQF BODIES Edward 'Emanuel'Sheldon, New York, N. Y. vApplication'May 7,-1952,,Serial No. 286,521 "9 Claims. ((173-675) re'late'toproducing signals'indicating the information desired but are not suitable for providing.two-dimensional or. three-dimensionallimages .of said information.

One primary object of "this invention is to provide means for producing twoor three dimensionalsupersonic images of theexamin cd body, as'distinguished from onedimensional signals produced by devices of the prior art.

The main problem in using supersonic waves for producing two-dimensional images for medical-diagnosis is 'th'edanger of causing damage to the patient by said radiation. The danger of over-exposure necessitates 'the ,use of "a relatively weak supersonic beam.

'The primary object of the present invention,1therefore, is to reduce the supersonic exposure necessary for producing a two-dimensional. supersonic image, which is very important'in .medical diagnosis. The living tissues are easily 'damaged by large ldosageof supersonic energy.

"In order to reduceithe supersonic exposure, ,I use in my invention the storageof supersonic images. The storage of supersonic images will allow examination of said images without the necessity of maintaining supersonic radiation during .the rea'dingtime. Asa result, a much smaller total dose ofsupersonic energy is necessary for examination of the human body or of other objects. The storage of supersonic images was accomplished ,by using a storage tube in which the supersonic image can be stored "in'thefonn of electrical "charges for a desired;time and thenmay be readas long as necessary. In another modification of this invention, the supersonic image is stored inthe supersonicimage pick-up tube, which is provided with a special storage target.

The purpose'sxofmy invention were accomplished by means of a novel system in whichthe supersonic beam is projected on theexamined body. The reflected or trans- 'mitted supersonic beam is modulated by 'the examined 'beamis produced by sender 1.

2 electrons of the returned beam, after multiplication, are converted over a suitable resistor into video signals.

"Video signals, after amplification byampIifiers are transmitted to the storage tube in which they are stored in the form of electrical charges. -When the stored supersonic image is tobe read, it is scanned by the reading electron beam. The reading electron beam is modulated by the stored image and is conver ted thereby into video signals.

The new video signals are now transmitted .to receivers,

which may be of kinescope type, facsimile type or ;electrographic camera type, to reproduce a visible image -for inspection or recording.

The invention will be better;understood when taken in ,connection with the accompanying drawings.

. target.

Figure 10 represents a modification of the storage tube. Figure 1d shows another modification -of -the storage 'tube.

Figure 2 represents a modification of -supersonic system.

'Figure'Za represents a modification;0f:supersonic-system in which conversion of supersonic images into electron image is obtained. I

Figure 2b represents a plan view of photoemissive :screen.

1 Figure 3 represents a modification of supersonic-image storagesystem using supersonicpickup storage tube.

"Figure 3a represents a'modification of the storage target for the tube illustrated in Fig. 3.

Figure 4 representsa cross-sectional view of supersonic image storage system in which a;refiected supersonic beam is used as an image-formingradiation.'

'Figure 5 representsa simplified modification of the storage system.

Figure 6 represents a plan viewof the storage target.

Reference will now be made to Fig. 1. The supersonic I The sender in this embodiment of invention'consists of'plurality of -pie zoelectric crystals 1a, 112,10, 1d, 1e, 1 etc., such as of qRochelle salt, tourmaline, or NH H PO known as ADP,

'KH 'PO known as KDP, 'KH AsO dipotas sium tartrate,

known as DKT, or ethylene diamine-tartrate, known-as EDT.

,Piezo-electric crystals may beef -varioussizesandcuts.

They should be selected to provide anequaland'homogeneous output-of supersonic energy, so that each crystal will produce the same qualityan'd quantityof supersonic waves when excited by a high frequency; source of potential. Quartz crystals usually canbe selected to be more similar to each other than other piezo-electric materials. In case the crystals 1a, 112, etc.- do not-have exactlythe same output, they shouldbebiased to equalize their output. Furthermore, improvement of theghomogeneity of the field may be obtained by using amosaic of small crystals. Such mosaic can'be made-by putting a plurality of small crystals together mechanically or by orientation of small piezo-electric crystals bymeans of supersonic waves. Each crystal in the se nder l has a metallic backing plate to provide a connection to'the source of electrical potential 3. The crystals with their backing plates are insulated from each other, so that each one forms an independentunit. The construction of a supersonic sender comprising a single ,piezo-electric crystal or a mosaic of such crystals, the mounting of piezo-electric crystals and the plating of said crystals .are-well..known -in :the art, as evigleneed by the; book entitled, Supersonics by Carlin, published by McGraw- Hill Company in 1949. It is believed therefore that further description of the supersonic sender is not necessary. The crystals are energized sequentially by said source of potential by means of commutator 3a revolving at the predetermined speed regulated by timer 4. In the preferred form of this invention, crystals of the sender 1 are not excited in turn one after another, but in such a manner that the crystal la is energized first, then the crystal 1 is energized, then again, crystal 1b. I dis- I covered that living tissues can stand much more of supersonic energy,if there is time interval between two irradiations. If we excited two adjacent crystals, such as 1a and 1b, one after another, then, due to overlapping of two supersonic beams from two adjacent crystals, the tissues exposed to radiation from the second adjacent crystal, will not have time to recover from the effect of the first supersonic beam and may be easily injured. On the other hand, if we energize after crystal 1a, the crystal 1 we irradiate different areas, which are separated from each other, and, therefore, the tissues have time to recover. The supersonic waves emitted from the energized crystal of the sender I spread transversely to form a broad lobe of acoustic energy. Such a lobe obviously cannot well be used for producing images with good definition and sharpness. Therefore, in my invention, I made use of acoustic lenses 5. The acoustic lenses may be of various forms and shapes, and it is to be understood that any device for focusing supersonic waves on the examined object may be used for the purposes of my invention.

One such modification, are Fresnel plates, which are known in the art and, therefore, it is believed that they do not have to be described in detail. The supersonic beam 6a from the crystal 1a is focused on the examined object 7. Instead of using lenses or mirrors, the sender crystals may be shaped to produce a parallel supersonic beam. In particular, a concave form of the crystal sender will be suitable for this purpose. Such parallel beam may be further focused by means of filters having a small aperture'for transmission of a fine supersonic beam.

The diagnostic possibilities of supersonic waves reside in their characteristic properties of being reflected at the boundaries of two media having a different modulus of elasticity. Various tissues, fluids and air have different reflections, transmission and absorption co-efficient values for supersonic waves. Therefore, the transmitted or reflected supersonic beam is modulated by the examined objects or tissues and carries information as to their pattern. For example, a cavity can be demonstrated inside of the body regardless of its thickness, a fluid or an air containing cavity may be shown, if present inside of the examined tissue.

A very important indication for the use of supersonic waves is diagnosis of brain tumors, especially if they impinge on ventricles in the brain and deform them. Ventricles of the brain contain normally cerobro-spinal fluid, which has different absorption, reflection and transmission properties for supersonic waves than the adjacent brain tissues. ventricles of the brain, it is necessary to inject into them air, in order to provide contrast for X-rays. The use of my invention will eliminate this difficult and sometimes dangerous procedure, as my device is able to visualize ventricles without injection of air. The supersonic beam 611 transmitted through the examined body 7 is now focused by means of an acoustic lens a on the novel supersonic image sensitive pick-up tube 9. The pick-up tube 9 has within it a target 10 of material responsive to supersonic waves, such as quartz, barium titanate, piezoelectric. ceramics, lithium sulphate, ADT, DKT or EDT. The target-cathode 10 may be formed of one large crystal, or may be in the form of a mosaic formed by plurality of small crystals. In some cases, it is preferable to evaporate piezo-electric material on a'dielectric base to At the present time, in order to visualize produce a very fine mosaic of crystals insulated from each other. The impingement of supersonic beam 6a on the target 10 causes a so-called reciprocal piezo-electric effect. As a result, an electric charge or potential appears on the surface of the target 10 in the region which was struck by supersonic beam. Duration of this electrical charge or potential is very short. If the supersonic beam has frequency in megacycles, the dielectric charge will persist only a few micro-seconds. The electron gun 11 produces the scanning electron beam 12. The electron beam 12 is deflected in two perpendicular to each other planes, by the deflecting yoke 14. The yoke is energized by generator producing saw-tooth waves. The scanning deflection system is well known in the art, and it is believed, therefore, that it does not have to be described in detail. The scanning electron beam 12 must reach the target 10 at the time when electrical charge on its surface is still present. The synchronization circuit 16 is provided to harmonize the activation of piezoelectric sender 1 with the activation of the electron beam 12. The electron beam 12 is slowed down in front of the target 10 by a decelerating electrode 15, which may be in the form of a ring electrode or of a mesh screen. Therefore, the electron beam 12 approaches the target 10 with a velocity close to zero volt. The scanning electron beam 12 is modulated by the charge image, having the pattern of supersonic image on the surface of the target 10. The electron beam 12a returns now to the electron gun 11 along its initial path, which is due to the action of uniform magnetic focusing field 20.. The returning beam 12a is modulated by said charge pattern on the target 10. The returning beam 12a strikes the v gun in the region around its defining aperture 21 and produces multiple secondary electrons. Therefore, the aperture disc 22 of the gun serves as the first stage of multiplier 23. The secondary electrons are directed into multi-stage multiplier 23. The multiplier 23 intensifies further said electrons by secondary electron emission. The output current from the final stage of the multiplier 23 is converted over a suitable resistor into video signals 30c and is fed into pre-amplifier and then into the amplifier in the usual manner. So far only the part of the image of the examined body was obtained, which corresponded to the supersonic beam 6a from the sender lta. Now the next sender 1 is activated. The electron beam is now synchronized with the supersonic beam 61. In this way, another fragment of the supersonic image is converted into video signals. This process continues until all supersonic senders have been activated and the whole image of the examined object has been produced in the form of video signals. In the preferred form of this invention, the activation of various senders does not occur in turn. After the sender 1a, the next sender to be activated is instead of the sender 1b, the sender If. I found that in this way the damage to the examined body by supersonic waves is considerably reduced. My explanation of this phenomenon is that by providing the space between irradiated areas of living tissues, I obtain a better dissipation of heat energy generated by the absorption of supersonic waves. In this way, the sensitive tissues of materials can better recover in the interval between supersonic energy pulses. Video signals having the pattern of the supersonic image after amplification are transmitted by high frequency waves or by a coaxial cable to receiver. Receivers may be of kinescope type 30, in which case, a screen of long persistence phosphor is necessary to reproduce the total image of the examined body, or a dark trace tube knownalso as a skiatron. For examination of immovable object, a facsimile receiver 30a can be used as well. The reproduced image may be enlarged as much-as necessary.

It is obvious that the sender, acoustic lenses, the examined body and the supersonic sensitive pick-up tube must be immersed in the liquid in order to reduce losses of supersonic energy. It is Preferable to use a highly dielectric medium such as oil for this purpose. The compartment containing oil and supersonic image storage system is not shown in order not to complicate drawings.

In order to obtain amplification'of contrast of the supersonic image, the amplifiers are provided with variable mu tubes in one or two stages. Small differences in intensity of the succeeding video signals are increased by variable mu tubes in non-linear manner, resulting in a gain of the contrast of the visible image in receivers.

The returning electron beam contains two groups of electrons. One group are-electrons which were reflected specnlarly from the target. Another one are electrons which were reflected nonspecularly, which means scattered. These two groups can be separated from each other before reaching the multiplier. There are many ways to separate these two groups of electrons, all well known in the art. The best method is to introduce an additional helical motion into the primary scanning beam 12, which means an additional transverse velocity. This is accomplished by the use of two electrodes disposed on both sides of the scanning beam 12., and which are provided with a positive potential from an extraneous source of electrical energy. The helical motion may also be produced in other ways, such as, for example, by misalignment of the electron gun 11 in relation to the axial focusing field. In such, case, the scattered electrons in the returning beam will be on one side of the specularly reflected electrons. Therefore, it will be possible to direct scattered electrons into the aperture of the multiplier, while stopping the reflected electrons by the edge of the multiplier aperture. The use of scattered electrons increases markedly sensitivity of the System, because it reduces the inherent shot noise of the scanning electron beam. The scattered electrons correspond to the areas of the picture which received a strong supersonic exposure, because such areas produce stronger charges or potentials in the target.

It is. obvious that the. above described supersonic image reproducing system may be used not only for the transmitted supersonic beam, but for the reflected or scattered supersonic beam as well. This system may be well used for magnification of supersonicimages and may serve therefore as a supersonic microscope.

I found that piezo-electric crystals exhibit a marked lack of uniformity as to their reverse piezo-electric effect.

It means that various areas of the same. crystals produce dilferent charges or potentials when impinged by the same supersonic beam. If such differences in output exceed. certain percentage of the signal, the value of reproduced image will be markedly impaired. In order to overcome this drawback, I eliminated the focusing lens 5a and I placed the pick-up tube 9 at such a distance from the examined object that the supersonic. beam 611 will, cover a substantial area of the. target 10 or all of the target 10 instead of being a beam of pin-point size. In this way, the charge or potential appearing on the surface of the target. will represent an integral of various charges of potentials corresponding to various points in the irradiated area. Therefore, the differences in piezoelectrical response will now be well equalized. For this modification of my invention, piezo-electric crystals of the target 10 should not have a high resistivity a e. g. quartz. Lithium sulphate will be suitable for this purpose. If the target 10 consists of a few crystals put up together to make a larger surface, there should be no insulation between separate crystals, in order to provide one conducting surface. In some cases, a metallic backing plate 10a should be provided on the side of the target 10 facing supersonic image. In such case, video signals produced by impingement of electron beam 12 on target 10 may also be taken off said layer 10a.

In this modification of my invention, the scanning electron beam 12 must be broad enough to cover the area of the target impinged by the supersonic beam. This can be accomplished by electron-optical means for factor of one hundred.

defocusing the electron beam, which are well known in the art. In this embodiment of my invention, the deflecting yoke 14 is markedly simplified as the broad electron beam needs only a small number of scanning motions to cover the entire target 10. In some cases, the deflection yoke may be eliminated completely.

The use of supersonic energy pulses, as described above also represents a great reduction of supersonic exposure to the examined body, which is of great importance in medical supersonic examinations. By using pulses of supersonic energy, the exposure of one image point of the examined body lasts only a few micro-seconds out of a frame time of /2()- /3() second.

The supersonic sender 1 may also operate continuously instead of by pulses from its various component crystals. In such case, the whole sender 1 is energized simultaneously. As a result, a broad supersonic beam is produced, which covers simultaneously the total area of the examined object. This system is not very suitable for examination of human bodies. As was explained above, the duration of potentials or charges produced by supersonic waves in the target 10 is only a few micro-seconds. The scanning electron beam 12 cannot in this short period of time scan all of the target 10, which would require 50-350,000 scans in a few micro-seconds, depending on resolution of the image desired. Therefore, in order to provide the charges or potentials on the surface of the target 10 for modulation of the scanning electron beam 12, it is necessary to continue supersonic exposure of the whole examined area for all the time of each frame. On the other hand, in the above described pulse system, each image point of the examined body has to be irradiated by supersonic energy for only a few microseconds during one frame time. This represents an increase of supersonic exposure by a factor of one thousand in the continuous method. As a result, the supersonic exposure, by using the continuous system will exceed the limits of safe exposure of the human body by a In industrial examinations in which there are no limitations as to the total dose of supersonic energy used, the system of continuous radiation may be used as well. In such case target 10 preferably should consist of a mosaic of crystals insulated from each other.

As was explained above, the main objective of the present invention is to provide means of storing supersonic images so that the supersonic exposure of image may be kept within limits of safety for the patient or for living tissues in general. A few watts of acoustic energy per 1 square centimeter can be considered the maximum safe dose. It is obvious that it is of utmost importance to reduce the supersonic exposure as much as possible in order to be able to examine the patient without causing any injury. The best solution of this problem is the removal of supersonic irradiation as soon as the supersonic image has been formed. This can be done only if the supersonic image can be stored for the desired period of time without maintaining the supersonic irradiation. I accomplished this objective by providing a novel system in which the supersonic image can be stored either in the supersonic pick-up tube or in the special intermediate storage tube or in the receiver tube. Besides, the system described above and illustrated in Fig. 1, if used without a storage tube, sulfers from two serious deficiencies. The first is that supersonic image when examining living tissues is very weak and therefore signal to noise ratio may be as low as 2 to 1, whereas for a satisfactory image a signal to noise ratio 10 to 1 is required. The second drawback is the necessity for the use of a phosphor of long persistence in the receiver, in the event there is no storage tube. This has serious limitations as to the brightness, contrast and sharpness of reproduced image. The brightness of image produced by persistent phosphors is so low that dark adaptation of eyes is necessary and the image has to be examined,

therefore, in a dark room which will considerably limit the usefulness of examination. These drawbacks are eliminated in my present system using the storage. In this embodiment of invention, video signals having the pattern of the examined object are sent from the pickup device 9 to a special storage tube 31, in which they can be stored for the required time in the form of charge images. In this way, the supersonic image can be assembled from fragments and can be stored in the storage starget 39 of the storage tube. When this image is to be read, the stored charge pattern may be reproduced as a visible image in the same storage tube or may be converted again into video signals. New video signals are now transmitted to regular kinescopes, in which they can be converted again into a visible image without any flicker and with any desired brightness. In this way, the need of a persistent phosphor in kinesoope is eliminated. My invention will also allow the improvement of signal to noise ratio of the system. It is known that if We have an image in which signal to noise ratio is below 10 to l, we can improve it by storing said image and by a gradual build-up of a stored image by superimposing a number of images one after another. It means, if we superimpose in the storage target one charge image having the pattern of the supersonic image after another, we will obtain a build-up image of much better signal to noise ratio than the original image.

In the embodiment of my invention illustrated in Fig. 1, video signals 300 having the pattern of supersonic image are transmitted after amplification by high frequency waves or by a coaxial cable to the novel storage tube 31.

Video signals c are transmitted to the storage tube 31 and modulate cathode ray beam 32 produced by the electron gun 33. The cathode 34 of the electron gun 33 is provided with a negative potential. The second anode 35 may be in the form of a conducting coating on the inside surface of the tube envelope, and is supplied with a positive potential in relation to the potential of the cathode of the electron gun. The proper operating potentials may be applied to the electrode of the electron gun from potential source 36. Between its terminals 37 and 38, a potentiometer or a bleeder resistance may be connected in order that the relative potentials of the various electrodes may be properly selected. The horizontal and vertical scanning motion of the electron beam 32 across the storage target 39 is provided by the deflection yoke 4-1 having horizontal and vertical deflection coils. The deflection coils are energized by a cyclically varying current of a suitable wave form, which may be obtained from a horizontal deflection generator and from a vertical deflection generator. Deflection generators are well known in the art and are, therefore, not shown in the drawings. The cathode ray beam 32 transforms video signals 31 into a stored charge image in the storage target 39.

The storage target 39, shown also in Fig. 6, consists of a thin perforated sheet of metal or other conducting material, or of a woven conducting wire mesh 39a. On

the side of the target facing the electron gun 40, there may be deposited by evaporation a thin coating to prevent leakage of charges. On the opposite side of the target 39, there is deposited a dielectric storage layer 3% in such a manner as not to obstruct the openings 390 therein. The scanning electron beam 32 is produced in the storage tube 31 by the electron gun 33, and is modulated by incoming video signals carrying the invisible supersonic image. This scanning electron beam 32 should have the finest spot compatible with the required intensity of beam. In some cases, between the electron gun 33 and the storage target 39 in close spacing to the target, there is mounted a fine mesh conducting screen for collecting secondary electrons emitted from the dielectric layer 3% when scanned by electron beam 32. As a result of the impingement of the scanning beam 32 on the storage target 39, there are deposited on the storage target varying charges at successive points according to the amplitude of modulating input signals. The best way of operating my system is to have the storage surface at zeropotential or at cathode potential and then to write on it positive, which means to deposit positive charges. This can be accomplished by adjusting the potential of the surface of the storage target, so that its secondary emission is greater than unity. The secondary electrons from the layer 3% will be collected by the collecting anode. or by an additional conducting mesh screen disposed in proximity of the storage target and positive charges will be left on the storage surface. These positive charges deposited on the storing surface of the target may be stored thereon for many hours depending on the type of the storage material 3% which was used. Whereas BaF has a time constant of 0.1 second, CaF has the time constant of 50 hours. Also, precipitated silica, silicon dioxide and titanium dioxide may be used for this purpose. The storage target must prevent fading of the stored image, which would cause its disappearance. It must also be free from lateral leakage of stored charges, which would impair resolution of the image.

These conditions are satisfied by equation:

ROAC=T in which i R0 is equal to resistivity of the target in ohm-cm. A=picture area in square centimeters C=capacitance of the storage target T =storage time for one image in seconds B=thickness of storage target in centimeters.

In case the storage time of three seconds is desired, the electrical resistivity of 5 X 10 ohm-cm. will be suitable, if the thickness of target is 10 cm. and picture element is l0 square centimeter.

When the stored image is to be read, the electron gun 33 is inactivated and instead, electron gun 40 is activated. The electron gun 40 produces a broad electron beam 41. The electron beam 41 is slowed down in front of the storage target 39 by decelerating electrode 42, which may be in the form of ring electrode or a fine mesh screen. The

passage of the broad electron beam 41 through the perforations in the target 39 is modulated by the pattern of deposited charges of said storage target. The greater the positive charge, the more electrons will pass through the openings 39c in the target. The less positive the stored charge, the fewer electrons will be transmitted through these openings. In this way, the electron beam 41 irradiating the storage target, will be modulated by the stored image. The transmitted electron beam 41a, therefore, will carry an image. This electron image is accelerated. The accelerating electrode 42 serves to accelerate transmitted electrons 41a to the fluorescent screen 43. The accelerating electrode may be in the form of a ring electrode or in the form of a conducting coating on the inside surface of the glass envelope. The accelerating electrode is provided with a positive potential from an external source of power, as described above.

Next, the electron image may be demagnified if its additional intensification is desired. The electron diminution of the image, in order to gain its intensification, is well known in the art and therefore does not have to be described in detail. The diminished electron image is projected on the fluorescent screen 43 at the end of the tube 31, where it can be viewed by the observer directly or by means of an optical magnifying eye-piece or may be photographed. The use of an optical eye-piece to magnify optically the electronically diminished image appearing on the fluorescent screen, is also well known in the art and therefore does not need further description. The fluorescent screen 43 is provided with an electrontransparent conducting backing 43a, such as of aluminum, which improves its eificiency.

On the other hand, if magnification of the supersonic image is needed,it can also be accomplished by electronoptical means. Therefore, my device can also be used as a supersonic microscope. Magnification of supersonic image may also be obtained in storage target 39.

After the stored image has been read and no further storage is desired, it may be erased by the use of the scanning electron beam 32 by adjusting the potential of the storage target to the value at which the secondary electron emission of its storing surface is below unity. In such case, the target will charge negatively to the potential of the electron gun cathode, and will neutralize the stored positive charges. The same results may also be obtained by changing velocity of the scanning electron beam 32.

A modification of the storage target is shown in Fig. 1a. In this embodiment of my invention, the storage target 45 is made of a perforated screen of dielectric material, such as glass, silicon dioxide or titanium dioxide. The dielectric material should have, preferably, electrical resistivity to satisfy the equation discussed above. The holes 45a in said screen can be produced by photoengraving methods. The preferred method is to use ionic or electronic etching. The openings must be uniform in size and spacing and should be, preferably, not larger than 100 microns, in diameter. The dielectric storage target may be attached to the walls of the tube by means of metallic rings, or it may be deposited on the mesh screen, as shown in Fig. 1. The supporting mesh screen in some cases may be made of insulating material instead of a conductive material. In some cases, a metallic fine mesh screen 46 connected to the source of potential can be placed in very close proximity to the storage target and then serves to collect secondary electrons emitted from the storage target under impingement of the scanning electron beam 32. Obviously, screen 46 must be disconnected from source of potential in the reading phase of operation when electron gun is activated.

In another modification of my invention shown in Fig. 1b, the storage target has a metallic backing 45b deposited on it in such a manner that the openings 45a re main unobstructed.

A simplified modification of my invention is shown in Fig. 1c. The storage tube 47 has only one electron gun 48. Video signals from the supersonic pick-up tube 9 modulate the electron beam 49. The perforated storage target may be the same as described above and illustrated in Figs. 1, 1a and 1b. The electron beam 49 modulated by incoming signals scans the storage target 39 in the usual television raster. The scanning motion of the electron beam is provided by deflecting yoke 14a, which has coils in two, perpendicular to each other, planes and which are energized by a saw-tooth signal generator. Theimpingement of the electron beam 49 on the target 39 produces secondary electron emission therefrom. The secondary electrons are drawn away either by an adjacent mesh screen or by a conductive coating on the wall of the tube. As a result, a positive charge image remains on the storing layer 39b.

In the second phase of operation, which is the reading phase, the electron gun 48 produces a broad, uncontrolled electron beam 50 covering substantially the whole area of the stored image. The broad electron beam is slowed down in front of the storage target 39 by decelerating electrode, which may be in the form of a ring electrode or in the form of a fine mesh screen 51. The screen 51 is connected to the source of an outside potential, and it is activated only in the reading phase of the operation. through the perforated target is controlled by charges stored in said target. Therefore, transmitted electron beam 50a will have the pattern of the stored charge image, which has the pattern of the invisible original image. The broad beam of electrons is accelerated and The passage of said broad electron beam 'of a scanning type.

10 is focused on the fluorescent screen 43 and reproduces a visible image thereon. Because of dielectric properties of the storage target, the charge image will persist there on for a very long time, dependent on the type of storage material used. During all this time, the invisible image can be reproduced in a visible form, as a fluorescent image, as was explained above. It is obvious that the storage tubes illustrated in Figs. 1, 1a, lb and 10 maybe used as well for converting the stored supersonic image into new video signals instead of reproducing said image in the fluorescent screen 43. This embodiment 58 of my invention is shown in Figs. 1d and 4, in which, instead of the fluorescent screen 43, there is disposed a multiplier 53. The electron beam 54 is in this modification The scanning deflection is provided by the deflection yoke 55. The electron beam scans the storage target in a television raster. The transmitted electrons 54a are fed successively into multiplier 53 by the action of the deflecting field 56. The electrons 54a after multiplication by secondary electron emission in the multiplier 53 are converted over a suitable resistor into video signals 47. Video signals 57 after amplification, are transmitted to receivers to reproduce the original supersonic image. Final reproduced supersonic image can be examined as long as the charge image is stored in the target 39 of the storage tube, without maintaining supersonic exposure. It is obvious that my invention can also be used for supersonic microscopy and diffraction studies.

Another modification of my invention is shown in Fig. 2. In this embodiment of my invention, the supersonic sender 1 is the same as was described above.

The novel supersonic pick-up tube has deposited on its Wall inside of said tube target 10 made of piezoelectric materials sensitive to supersonic waves as described above. The target 10 has property of becoming conductive and producing a current of electrical charges .and pattern of potentials thereon in response to said supersonic radiation. The target 10 in this embodiment of invention should be preferably in the form of a mosaic of piezo-electric crystals which are insulated from each other. Quartz will be very suitable for this purpose because of its high electrical resistance, but other piezoelectric materials described above may also be used. In some cases, on the side of the target 10 facing the supersonic image there is deposited a thin dielectric layer in order to improve insulation of crystals forming the mosaic target 10.

In close spacing, such as a few microns, from the target 10, there is mounted a composite, perforated screen 60 consisting of a fine mesh screen 60a of conducting material. On said mesh, there is deposited a p'hotoemissive layer 6%, such as of CsOAg, cesium, potassium or lithium or antimony or bismuth, in such a manner as not to obstruct the openings 60c in the mesh screen 60a. A plan view of this screen is shown in Fig. 2b. The pattern of the electrical charges on the target 10 can be considered as a pattern of various potentials or electrical fields. I discovered that these potentials will modulate the emission of photoelectrons from the photoemissive layer 60b, although they are behind said layer. The layer 60b is irradiated by a source of light 64 and produces a strong beam of photoelectrons. The emission of photoelectrons from layer 60b depends on electrical fields in its proximity. The more positive the charges on the target 10, the more suppressed will be the emission of photoelectrons from layer 60b. In this way the photoelectron beam is modulated by the charges in the target 10, which have the pattern of the original supersonic image. The mesh screen 60a and photoemissive layer 60b may be also deposited directly on the target 10 instead of being separated.

The photoelectron beam 60d emitted from the layer I 60b is focused by fields 63 and can be further intensified by acceleration by electrostatic or by electromagnetic fields 62, as well as by electron-optical demagnification.

Acceleration of electrons and electron-optical demagnification of electron image are well known in the art and therefore, it is believed, they do not have to be described in detail. The intensified photoelectron image is projected on the storage target 64, which is of a semi-conductor such as glass. The photoelectron beam strikes target 64 with velocity, at which the secondary emission of the target is greater than unity. The emitted secondary electrons are drawn away by the adjacent mesh screen 64a. A a result, a positive charge pattern remains stored in target 64. As the target 64 is very thin and has semiconductive properties, the charge can pass through it and appears on the opposite side of the target, which faces electron gun 65. Electron gun 65 produces a fine beam 66 of electrons. The electron beam 66 is focused by electrostatic or electromagnetic focusing coil 67 and by an alignment coil 67a and is deflected into two directions perpendicular to each other by deflection coils 68, so that it scans target 64 in a television-like raster. The electron beam 66 is decelerated in front of the target 84 by a ring electrode 64b. Also,- a mesh screen may be used for this purpose. Target 64 has stored on its surface a pattern of electrical charges having the pattern of the original supersonic image. The scanning beam 66 neutralizes these stored positive charges. The returning electron beam 66a is, therefore, modulated by said charges and carries video information. The returning electron beam strikes the first stage 69a of the electron multiplier 69. The secondary electrons from the first stage of the multiplier strike the succeeding stage around and in the back of the first stage. This process is repeated in a few stages resulting in a marked multiplication of the original electron signals. The signal currents from the last stage of the multiplier are converted :over a suitable resistor into video signals and are fed into amplifiers. After amplification, they are sent by coaxial cable or by high frequency waves to the receivers of kinescope type 30, dark trace tube, known also as a skiatron type 30b or to facsimile type 30a, in which they are reconverted into a visible image for inspection or for recording. The photoemissive layer 6011 may also be in the form of a mosaic. In such case, a dielectric layer should be interposed between the layer 60b and the layer 60a. The light irradiation of said mosaic layer causes emission of photoelectrons. As a result, a positive charge image remains on the mosaic. This charge image is scanned by the electron beam 66 and modulates said beam, as was explained above. Video signals may be taken off the conducting screen 60a or may be obtained from the multipliers 69.

The pick-up tube 70 may also serve for storage of supersonic images if the energy of the scanning electron beam 66 is selected, so that it is not sufficiently strong to neutralize the electrical charges on the target 64 in one scan. With proper selection of intensity of the scanning beam 66 and of the capacity and resistance of target 64, r

the charge image can be stored in said target for many seconds. It is also obvious that the fraction of the scattered electrons in the returning electron beam 66a, which is modulated by the supersonic image, may be separated from the other electrons of said beam. If only this fraction of electrons is used for producing video signals, the signal to noise ratio of the entire system will be markedly improved.

Another modification of my invention is shown in Fig. 2a. The supersonic image sensitive pick-up tube 70a has perforated composite target 71. The composite cathode 71 in this embodiment of my invention consists of a perforated conducting screen 71a on which is deposited the photoemissive layer 71b and supersonic radiation sensitive layer 71c. Both layers 71b and 710 are deposited in such a manner as not to obstruct the openings in the perforated mesh screen 71a. The composite screen 71 is deposited on the wall of the pick-up tube 70a within said tube. The mesh screen 71a may be of aluminum, gold, platinum or silver. The photoemissive layer may be of CsOAg, Sb Cs or other photoemissive materials. The supersonic sensitive layer 710 may be of piezo-electric crystals described above and should be preferably of crystals having dielectric properties such as quartz and should also be preferably of mosaic type. If the supersonic sensitive layer 710 is deposited on the side of the conducting layer 71a nearer to the source of supersonic beam, an insulating layer, such as of enamel, mica or plastic 7111 may be provided to separate said supersonic sensitive layer 71c from the conducting mesh screen 71a. Instead of an insulating layer 71d, the mesh screen 71a may have an insulating coating applied to its surface adjacent to the supersonic sensitive layer 710. On the other hand, if the supersonic sensitive layer 710 is deposited on the photoemissive layer 71b, there is no need for an additional insulating layer, because the photoemissive layer has high resistance and separates the supersonic sensitive layer from the conducting screen 71a.

The screen 71a is irradiated by the source of light 61 simultaneously with the supersonic exposure. The light causes emission of photoelectrons 73 from the photoemissive layer 71b. The emission of photoelectrons is controlled by the pattern of potentials present on the supersonic layer 710, which corresponds to the original supersonic image. Furthermore, the passage of photoelectrons from the layer 71b through the perforated layer 71c depends on potentials present around the openings therein. Therefore, the transmitted electron beam 73 in this arrangement is twice modulated by the pattern of said potentials and will also have the pattern of the original invisible supersonic image. The emitted photo-electron beam 73 is now accelerated, is electron-optically diminished and is focused on the secondary electron emitting semi-conducting target 64 described above and illustrated in Fig. 2 and is stored there. The rest of the operation of this pick-up tube 70a is the same as described above and illustrated in Fig. 2. The electron image stored in the target 64 is scanned by an electron beam and is converted into video signals. Video signals are, after amplification, transmitted to receivers 30 or 30a for reproducing visible images.

It is obvious that the sender, acoustic lenses, the examined body and the supersonic sensitive pick-up tube must be immersed in the liquid in order to reduce losses of supersonic energy. It is preferable to use a highly dielectric medium, such as oil for this purpose. The compartment containing oil and supersonic image storage system is not shown in order not to complicate drawings.

It is obvious that the above described supersonic image reproducing system may be used not only for the transmitted supersonic beam, but for the reflected or scattered supersonic beam as Well.

The sender 1 may also consist of one or a few crystals only if it is used in combination with rotating disc or drum provided with multiple small apertures.

The supersonic beam from the sender is then transmitted in succession through said apertures and is reduced thereby each time to a fine beam. The rotating filter should be of material which causes no reflection of the stopped portion of the supersonic beam, such as of rubber. The transmitted fine supersonic beam impinges successively on adjacent areas of the examined body and produces each time a supersonic image point. This simplified form of the sender may be used with any of pick-up tubes illustrated in Figs. 1 to 5..

it is obvious that my invention may be also used for supersonic microscopy. The invisible supersonic image of the examined body is converted into an electrical potential image or into an electron image. The latter images are converted again into electrical signals, as was explained above. The electrical signals can be used to reproduce the invisible image with any desired degree of magnification by the use of suitable electron-optical fields or deflection circuits. This may be accomplished by -posited charges on said storage target.

13 enlarging said image in any of the storage tubes described above or in any of the receivers.

It should also be understood that any of the pick-up tubes illustrated in Figs. 1 to 5 may be also used for receivmg infra-red images, provided that the cathode or its modifications in said tubes is of a material sensitive to infra-red radiation, such as barium titanate, titanium dioxide, ceramics or others. In such a case, my inventlon may serve also as a system for reproducing infra-red images of various infra-red wave lengths, or it may also serve as an infra-red microscope. In this event polarizing potential should be provided across infrared sensitive layer.

Another modification of my invention is shown in Fig. 3. In this embodiment of my invention, the superv sonic image is picked up and stored in the same tube.

This modification has the advantage of being more economical in "construction. The novel pick-up and storage tube 100 has supersonic image sensitive cathode 10 described above. In some cases, the cathode 10 has a conducting backing 10a on the side facing the supersonic image. The supersonic beam carrying the image of the examined body impinges on the cathode and produces therein a pattern of electrical charges or potentials corresponding to the supersonic image. In this operation of my device, the cathode 10 must be of high resistivity, so that the changes produced on its surface by the supersonic image will not suffer from lateral leakage. A suitable material in such case will be quartz. This electrical pattern is scanned by the broad electron beam 101 from the electron gun 102. The electron beam may be defocused at its defining aperture 103, or it may be defocused by the action of magnetic or electrostatic fields 104, after passage through the aperture 108 in the electrode 106. The broad electron beam 101 is decelerated in front of the cathode 10 by the action of decelerating electrode 107, which may be in the form of a ring electrode or of a mesh screen. The electron beam 101, after being modulated by the charge pattern on the free surface of the cathode 10, returns through the aperture 108. The returning beam 101:: is bent by the action of the magnetic or electromagnetic fields 100a and is projected on the perforated storage target 39, which was described above.

Further intensification of the returning electron beam 101a may be obtained by acceleration and electron-0ptical diminution. The electron-optical dem-agnification is accomplished by means of magnetic or electrostatic fields and is well known in the art. The action of the electron gun 102 must be synchronized with the action of the supersonic sender so that the electron beam 101 will arrive to the cathode 10 at the time when the supersonic induced charge image is present thereon. The action of electron gun 102 should preferably be intermittent, so that the returning electron beam 101a can be accelerated and projected on the storage target 39 without interference from the incoming electron beam 101. The returning broad electron beam 101a strikes the storing layer 3% of the target 39 and produces secondary electron emission therefrom. As a result, a positive or negative charge remains stored on the dielectric layer 39b. In the next phase of the operation, which is the reading phase, the electron gun 104 is activated, whereas the electron gun 102 is inactive now. The electron gun 104 pro 'duces a broad electron beam 105. The beam 105 is slowed down in front of the storage target 39 by the action of decelerating electrode 111, which may be in the form of a ring electrode or of a mesh screen. The passage of the broad electron beam 105 through the perforated target 39 is modulated by the pattern of de- The greater the positive charge, the more electrons will pass through the openings 39c in the target. The less positive the stored charge, the fewer electrons will be transmitted through these openings. In this way, the electron beam 105 irradiating the storage target will be modulated by the stored image. The transmitted electron beam 105a, therefore,

14 will carry an image. This electron image is accelerated. The accelerating electrode 110 serves to accelerate transmitted electrons 105a to the fluorescent screen 107. The accelerating electrode may be in the form of a ring electrode or in the form of a conducting coating such as of Aquadag on the electrodes 106 and 106a. The accelerating electrodes are provided with a positive potential from an external source of power, as described above. Instead of fluorescent screen 107, an opacifying screen, such as used in dark trace tube, may be used as well.

Next, the electron image may be demagnified if its additional intensification is desired. The electron diminution of the image, in order to gain its intensification, is well known in the art and, therefore, does not have to be described in detail. The diminished electron image is projected on the fluorescent screen 107, where it can be viewed by the observer directly or by means of an optical magnifying eye-piece or may be photographed. The use of an optical eye-piece to magnify optically the electronically diminished image appearing on the fluorescent screen, is also well. known in the art and, therefore, does not need further description. The fluorescent screen 107 is provided wih an electron-transparent conducting backing, such as of aluminum 107a, which improves its efficiency. It is obvious that as long as the charge image persists on the storage target 39, the fluorescent image 109 can be reproduced.

After the stored image has been read and no further storage is desired, it may be erased by the use of the electron beam 101 by adjusting the potential of the storage target to the value at which the secondary electron emission of its storing surface is below unity. In such case, the target will charge negatively to the potential of the electron gun cathode, and will neutralize the stored positive charges. The same results may also be obtained by changing velocity of the electron beam 101.

A modification of the storage target is shown in Fig. 3a. In this embodiment of my invention, the storage target 39 is made of a perforated screen 111 of dielectric material, such as glass, silicon, dioxide or titanium dioxide. The dielectric material should have, preferably, electrical resistance to satisfy the equation discussed above. The holes 111a in said screen can be produced by photoengraving methods. The preferred method is to use ionic or electronic etching. The openings must be uniform in size and spacing and should be, preferably, not larger than microns in diameter. The dielectric storage target may be attached to the walls of the tube by means of metallic rings, or it may be deposited on the mesh screen, as shown in Fig. 1. The supporting mesh screen in some cases may be made of insulating material instead of a conductive material. In some cases, 'a metallic fine mesh screen 112 connected to the source of potential can be placed in very close proximity to the storage target and then serves to collect secondary electrons emitted from the storage target under impingement of the electron beam 101a. Obviously, screen 112 must be disconnected from source of potential in the reading phase of operation when electron gun 104 is activated.

In another modification of my invention, the storage target 111 has a metallic backing layer deposited on it in such a manner that the openings 111a remain unobstructed.

Instead of reproducing the supersonic image in the pick-up tube 100, we may also convert the stored charge image in the target 39 into video signals, as was explained above. In this modification of my invention, the broad electron beam is replaced by the scanning electron beam. The transmitted scanning beam is collected by the collector electrode and is converted into video signals over a suitable resistor in the usual manner. Also, the non-transmitted returning electron beam 105b may be used for producing video signals. The returning electron beam 105b may be intensified by multiplier 104abefore its conversion into video signals.

by it on the cathode 10 represents, therefore, only one image point. The supersonic beam representing one image point is made broad enough to cover 'a substantial part or all of the cathode 10. Therefore, the charge or potential appearing on the surface of the target 10 will represent an integral of various charges of potentials corresponding to various points in the irradiated area. In this way, the differences in piezo-electrical response will be well equalized. If the cathode 10 consists of a few crystals put up together to make a larger surface, there should be no insulation between separate crystals in order to provide one conducting surface. In some cases, a metallic backing plate should be provided on the side of the cathode 10 facing supersonic image. In this modification of my invention, the electron beam 101 must be broad enough to cover the area of the target impinged by the supersonic beam. This can be accomplished by electron optical means for defocusingthe electron beam which are well known in the art. In this embodiment of invention, the deflecting yoke is markedly simplified as the broad electron beam needs only a small number of .scanning motions to cover the entire cathode 10.

In some cases, the deflection yoke may be eliminated completely. The electron beam 101 is modulated by said charge or potential on the cathode 10. The returning modulated electron beam 101a stores this information on the storage target 39. This process is repeated in successive irradiations until all image points have been reproduced as charge images and have been assembled on the storage target 39. Then begins the reading phase of the operation, which is the same as was described above.

It is obvious that the sender, acoustic lenses the examined body and the supersonic sensitive pick-up tube must be immersed in the liquid in order to reduce losses of supersonic energy. It is preferable to use a highly dielectric medium, such as oil for this purpose. The compartment containing oil and supersonic image storage system is not shown in order not to complicate drawmgs.

It is obvious that the above described supersonic image reproducing system may be used not only for the transmitted supersonic beam, but for the reflected or scattered supersonic beam as well.

Another modification of my invention is shown in Fig. 4. In this embodiment of invention, the function of supersonic sender and pick-up tube are performed by one and the same tube. target 86, which is made of a plurality of piezo-electric crystals, such as quartz, barium titanate, ADP, DKT, EDT, lithium sulphate or other piezo-electric materials. Each crystal has deposited thereon a conducting layer 86b, such as of metal. of the tube 85 on its wall. The piezo-electric layer 86a may be made of one single large crystal or, preferably, may be made in the form of a mosaic of small crystals 36A, 86B, 86C, 86D, 86E, etc. Each of said crystals is connected separately to the source of potential 87. They are energized sequentially by the action of commutator, as was explained above. The commutator is controlled by the timer 4-. The supersonic beam 88A produced by crystal 86A is focused by the acoustic lens 88 on the examined body. As was explained above, supersonic waves are reflected at the boundary of two different materials. Therefore, reflected supersonic waves are modulated by the examined body and carry its invisible image. The reflected supersonic beam 89A returns to the sender crystal 86A. The crystal 86A is now disconnected from the The novel sender-pick-up tube 85 has The target 86 is deposited inside source of potential 87 by the action of commutator. The returning supersonic beam 89A impinging on its sender crystal 86A produces therein a pattern of potentials or charges due to reverse piezo-electric effect. This pattern of charges or potentials is of very short duration, such as a few micro-seconds. The electron gun 90 is activated now and produces the scanning electron beam 91. The electron beam 91 is slowed down in front of the target 86 by decelerating electrode, which may be in the form of a ring electrode or of a mesh screen 15a. The electron beam 91 must arrive to the crystal 86A at the time when the pattern of charges is present thereon. Synchronization circuit serves to harmonize the action of the scanning electron beam 91 with the return of supersonic beam 89A. This method of operation has the following advantage. The spurious reflections of supersonic waves may be eliminated by my device. It meansif we know that the investigated area is a certain distance from the sender, we may calculate the time necessary for supersonic waves to return from this area and will energize the electron beam 91 according to this time. In such a case, all supersonic waves reflected from objects at different planes than the investigated one will be ignored by the pick-up tube and will not interfere with the image. After the crystal 86A has been read by electron beam 91, we energize another crystal of the sender tube, e. g. 86F. The sender preferably should not be energized until all supersonic waves reflected by the most distant plane of the examined object passed away in order to avoid their interference with the new supersonic waves to be sent by the next energized crystal. The electron beam 91 approaches the target 86 with a velocity close to zero volt. The scanning electron beam 91 is modulated by the charge image having the pattern of supersonic image on the surface of the target 86. As a result, the returning beam 91a is modulated by said charge pattern on the target 86. The electron beam 91a returns now to the electron gun along its initial path, which is due to the action of uniform magnetic focusing field 92. The returning beam strikes the gun in the region around its defining aperture 90a and produces multiple secondary electrons. The aperture disc 90b of the gun serves, therefore, as the first stage of multiplier 93. The secondary electrons are directed now into multi-stage multiplier 93. The multiplier 93 intensifies further said electrons by secondary electron emission. The output current from the final stage of the multiplier 93 is converted by a suitable resistor into video signals. Video signals are fed into pre-amplifier and then into the amplifier in the usual manner. The amplified video signals from the sender-pick-up tube 85 having the pattern of the examined object, are now transmitted to the storage tube 31 or 58, as was explained above. It is obvious that any modification of the storage tubes described above may be used in connection with this novel sender-receiver 85.

It is obvious that the supersonic sender-pick-up tube 85, the examing body and the lenses should be immersed in a compartment containing liquid, preferably such as of dielectric oil in order to avoid losses of supersonic energy. The tube 85 obviously must be rugged and free from microphonics.

A simplified form of my invention is shown in Fig. 5. The supersonic image produced by the sender 1 is projected in this embodiment of the invention on supersonic waves sensitive receiver 115. The receiver consists of a thin plate 116 of supersonic sensitive material, such as quartz, barium titanate, ADP, EDP, lithium sulphate or other piezo-electric materials. The piezo-electric plate 116 has a metallic backing 116a. The supersonic sensitive layer may be made of one large crystal or of a mosaic of plurality 'of small crystals, which may be put together mechanically or which may be properly oriented by supersonic waves. It may also have a micr0crystaline structure. The supersonic images produce in the layer 116 of said receiver 115 electrical charges or potentials due to reverse piezo-electric effect. The signals can be 17 taken oi the metallic layer 116:: and may be fed into pre-amplifier and then into amplifier. The amplified signals aretransmitted to one of the storage tubes described above and illustrated in Figs. 1, 1a, 1b, or 1d. This system should preferably operate with a broad supersonic beam representing one image point of the examined body, in order to eliminate non-uniformity of the response of piezo-electric crystals. The signals representing various image points are stored as charges and are assembled in the storage target 39 or other storage target of the storage tube, according to the pattern of supersonic image. The rest of the operation of this system is the same as was described above, in Figure 1.

This supersonic system has the advantages of simplicity. It is not as sensitive as other systems described above, because it has a much higher noise. In particular, the noise in this system will be the noise of the amplifier, which is about 2 micro-volts. On the other hand, the noise of the systems illustrated in Figs. 1, 2, 3 or 4 is much lower, being a noise of the scanning electron beam.

It is obvious that the sender, acoustic lenses, the examined body and the supersonic sensitive pick-up device must be immersed in the liquid in order to reduce losses of supersonic energy. It is preferable to use a highly dielectric medium such as oil for this purpose. The compartment containing oil and supersonic image storage system is not shown in order not to complicate drawings.

It is obvious that the above described supersonic image reproducing systems may be used not only for the transmitted supersonic beam, but for the reflected or scattered supersonic beam as well. They may be also used for supersonic microscopy, diiffraction studies or spectroscopy.

As various possible embodiments might be made of the above invention, and as various changes might be made in the embodiment above set forth, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. A device for reproducing supersonic images comprising in combination an examined body a source of supersonic radiation for irradiating said body and producing a supersonic image of said body, a vacuum tube having piezo-electric means sensitive to supersonic radiation, said piezo-electric means receiving said supersonic image and converting said image into an electrical pattern, said piezo-electric means being furthermore supported by the wall of said tube, means for producing a broad non-scanning beam of electrons, said beam being modulated by said electrical pattern on said piezo-electric means and means spaced apart from said piezo-electric means for receiving said modulated broad electron beam.

2. A device as defined in claim 1 in which said piezoelectric means comprise a plurality of supersonic radiation sensitive elements separated from each other.

3. A device for reproducing supersonic images comprising in combination an examined body a source of supersonic radiation for irradiating said examined body and producing a supersonic image of said body, a vacuum tube having piezo-electric means sensitive to supersonic radiation, said piezo-electric means receiving said supersonic image and converting said image into an electrical pattern, said piezo-electric means being furthermore supported by the wall of said tube, means for producing a broad non-scanning beam of electrons, said beam being modulated by said electrical pattern on said piezo-electric means and means for receiving and converting said modulated broad electron beam into electrical signals and means for storing said electrical signals.

4. A device for reproducing supersonic images comprising in combination an examined body a source of supersonic radiation for irradiating said body and producing a supersonic image of said body, a vacuum tube having piezo-electric means sensitive to supersonic radiation, said piezo-electric means receiving said supersonic image and converting said image into an electrical pattern, said piezo-electric means furthermore being disposed with their back and front surfaces inside said tube and being supported by the end-wall of said tube, means for producing a broad non-scanning beam of electrons, said broad beam being modulated by said electrical pattern on said piezo-electric means and means for receiving said modulated broad electron beam.

5. A device as defined in claim 1, in which said piezoelectric means are in contact with the wall of said tube.

6. A device for reproducing supersonic images comprising in combination an examined body a source of supersonic radiation for irradiating said examined body and producing a supersonic image of said body, a vacuum tube having piezo-electric means sensitive to supersonic radiation, said piezo-electric means receiving said supersonic image and converting said image into an electrical pattern, said piezo-electric means being furthermore supported by the wall of said tube, means for producing a broad non-scanning beam of electrons, said beam being modulated by said electrical pattern on said piezoelectric means and means for receiving and converting said modulated broad electron beam into electrical signals, said means receiving and converting said electron beam into electrical signals comprising a target for receiving said modulated broad electron beam, means for producing a scanning electron beam to scan across said target and means for decelerating said scanning electron beam disposed in proximity of said target, and means for receiving said electrical signals.

7. A device as defined in claim 6, in which said piezoelectric means comprise a plurality of supersonic radiation sensitive elements separated from each other.

8. A device as defined in claim 6, which comprises in addition means for storing said electrical signals, said means being disposed outside of said vacuum tube and being connected to said vacuum tube.

9. A device as defined in claim 6, which comprises means returning said electron beam after scanning said target and means for deriving said electrical signals from said returning scanning beam.

References Cited in the file of this patent UNITED STATES PATENTS 2,164,125 Sokoloff June 27, 1939 2,453,502 Dimmick Nov. 9, 1948 2,528,725 Rines Nov. 7, 1950 

